It is known in the photographic field to use image dye-providing compounds in photographic elements, such as image transfer type film units. For example, illustrative diffusible color couplers are described in U.S. Pat. No. 2,698,244, granted to Land. With such couplers, dyes are synthesized in an image-receiving layer. U.S. Pat. No. 2,774,668 discloses use of mobile dyes previously-formed by reaction of a coupler with a mobile oxidized color developer. Another disclosure as to the use of a mobile previously-formed dye is found in U.S. Pat. No. 2,983,606, granted to Rogers. However, initially mobile image dye-providing compounds cause some disadvantages when used in a photographic element. Particularly, in such photographic elements, diffusion into an adjacent layer is in some cases so fast that detrimental influences result on the interimage effect and color reproduction.
Image dye-providing compounds which are initially immobile in a photographic element, i.e., stabilized image dye-providing compounds, solve various problems encountered in the case of using initially mobile compounds. These dye-providing compounds may be temporarily stabilized by using a heavy metal counter ion such as barium salt disclosed in U.S. Pat. No. 2,756,142, granted to Yutzy. They may contain a removable ballast group, as described in Whitmore's Canadian Pat. No. 602,607, and U.S. Pat. Nos. 3,227,552, 3,628,952, 3,728,113, 3,725,062, etc. U.S. Pat. Nos. 3,443,939, 3,443,940, 3,443,941, and 3,751,406 disclose compounds capable of undergoing intramolecular cyclization by oxidation to split off a dye. These compounds undergo an oxidative cyclization reaction during the development processing to split off an "initially formed dye moiety". Such compounds can be classified into two groups. Compounds belonging to one group are those for which an ordinary color developer is used in development processing, i.e., which undergo coupling reaction with an oxidation product of the above-described color developer to split off a diffusible "initially formed dye moiety" by the subsequent ring-closing reaction. Compounds belonging to another group are those which constitute a silver halide-developing agent, and undergo a ring-closing reaction in the absence of other developing compounds to split off a diffusible dye. However, this second diffusible dye is split off in a form containing a sulfinic acid group. This sulfinic acid group is comparatively chemically active, and causes chemical action with various additives or silver halide in a photographic element to exert detrimental influences on the final image.
Japanese Patent Application (OPI) No. 33826/73 (Fleckenstein et al) discloses immobile compounds which undergo redox reaction and then alkali cleavage to release a dye, and Japanese Patent Application (OPI) No. 113624/76 (Koyama et al) discloses other immobile compounds capable of releasing a dye based on the same mechanism. However, these image dye-providing compounds split off diffusible dyes where they undergo oxidation reaction, and hence the use of a direct positive silver halide emulsion or other reversal mechanism is required for obtaining a direct positive image. In addition, a serious defect with this system is that the two processes of oxidation and alkali hydrolysis must be conducted before release of the dye, resulting in a seriously prolonged image-completing time.
Attempts to directly obtain a positive image by using a negative emulsion are disclosed in Japanese Patent Application (OPI) Nos. 111628/74 and 4819/77 (Hinshaw et al) and Japanese Patent Application (OPI) No. 63618/76 (Field et al).
The compounds described in the above-described patents are immobile, and they release, in a reduced state, a diffusible, photographically useful group by intramolecular nucleophilic reaction in the presence of alkali. These compounds can be oxidized by redox reaction in a photographic element, and, as a result, the rate of splitting off of the photographically useful group may be substantially decreased.
The compounds described in the above patents can overcome many defects which are inherent in conventional initially-immobile compounds. However, there still exists many problems of fogging and deterioration of discrimination due to the timing lag between oxidation and alkali hydrolysis (which are in competitive relation with each other in the photographic element), poor diffusibility of released dyes due to the absence of water-soluble groups in released dyes, elimination of mordanted dye, etc.